Technical Field
This disclosure relates to electronic circuits. More specifically, this disclosure relates to a coupling inductor based hybrid millimeter (mm)-wave switch.
Related Art
For mm-wave applications, e.g., passive imaging, short-range communication, and sensing, etc., switches are essential components for transmitting-receiving functions, signal-routing, and modulation. For example, see (1) M. Uzunkol and G. M. Rebeiz, “A Low-Loss 50-70 GHz SPDT Switch in 90 nm CMOS,” IEEE J. Solid-State Circuits, vol. 45, no. 10, pp. 2003-2007, October 2010 (hereinafter “Uzunkol”), (2) S.-F. Chao, et al, “A 50 to 94-GHz CMOS SPDT Switch Using Traveling-Wave Concept,” IEEE Microw. Wirel. Compon. Lett., vol. 17, no. 2, pp. 130-132, February 2007 (hereinafter “Chao”), and (3) J. He, et al, “Analysis and Design of 60-GHz SPDT Switch in 130-nm CMOS,” IEEE Trans. Microw. Theory Tech., vol. 60, no. 10, pp. 3113-3119, October 2012 (hereinafter “He”).
Switches can have one or more input ports and one or more output ports. For example, a single-pole single-throw (SPST) switch has a single input port and a single output port, and the switch can be in one of two states: open (the input port is electrically disconnected from the output port) or closed (the input port is electrically connected to the output port). The important specifications of a switch include, inter alia, insertion loss, return loss, isolation, and power handling ability. Insertion loss refers to the loss (e.g., voltage drop, power loss, etc.) that is introduced by the switch between the input port and the output port. Return loss is a measure of the power of the reflected signal, i.e., the power of the signal that is reflected back at the input port. Note that return loss is a component of insertion loss; the higher is the return loss of a switch, the higher is its insertion loss. Isolation refers to the ability of the switch to prevent power leakage from the input port to the output port when the input port is electrically disconnected from the output port. Power handling ability refers to the upper bound of the range of input power values over which the output power of the switch increases linearly with the input power. Power handling ability can be represented by the so-called “input-referred 1-dB compression point,” which is defined as the input power that causes a 1 dB drop in the output power with respect to the linear gain due to device saturation. For example, let us assume that, at an input power of x dB, the output power of the switch is expected to be y dB based on the linear gain of the switch. However, suppose the actual output power of the switch is (y−1) dB instead of y dB. Then, x dB is the “input-referred 1-dB compression point” for the switch.
A series-shunt switch architecture is traditionally used for switches that operate in the radio frequency (RF) bands. In contrast, for mm-wave switches, conventional architectures remove the series switch to reduce insertion loss (e.g., see Uzunkol and Chao). However, isolation performance degrades without the series switches. Therefore, what are needed are switches that have low return loss, low insertion loss, high isolation, and high power handling ability over a wide range of mm-wave frequencies.